In electric power transmission and distribution networks, fault current conditions may occur. A fault current condition is an abrupt surge in the current flowing through the network caused by faults or short circuits in the network. Causes of the faults may include lightning striking the network, and downing and grounding of the transmission power lines due to severe weather or falling trees. When faults occur, a large load appears instantaneously. The network, in response, delivers a large amount of current (i.e. overcurrent) to this load or, in this case, the faults. This surge or fault current condition is undesirable as the condition may damage the network or equipments connected to the network. In particular, the network and the equipments connected thereto may burn or, in some cases, explode.
One of the systems used to protect power equipments from damages caused by fault currents is a circuit breaker. When a fault current is detected, the circuit breaker mechanically opens the circuit and disrupts the overcurrent from flowing.
Another system to limit the fault current is a superconducting fault current limiter (“SCFCL”). Generally, a SCFCL comprises a superconducting circuit that exhibits almost zero resistivity below critical temperature level Tc, critical magnetic field level Hc, and critical current level Ic. If at least one of the conditions is raised above the critical level, the circuit becomes quenched and exhibits resistivity.
During normal operation, superconducting circuit of SCFCL is maintained below Tc, Hc, and Ic. During fault, one or more the conditions is raised above the critical level Tc, Hc, and Ic. Instantaneously, the superconducting circuit in the SCFCL is quenched and its resistance surges, thereby limiting transmission of the fault current. Following some time delay and after the short circuit fault is cleared, To, Ho, and Io are returned to normal values and current is transmitted through the network and the SCFCL.
The superconducting fault current limiters used currently in power transmission network, although capable of limiting fault currents, are not adequate. For example, SCFCL are incapable of supporting high voltage transmission networks. In addition, conventional SCFCL requires large footprint due to its technical deficiencies. Accordingly, a new type of SCFCL is needed.